Objectives: The purpose of this study was to evaluate the effect of waiting interval on the chemical activation of dual-cure one-step self-etching adhesives before placing resin core materials on the regional bond strength to root canal dentin.
Materials and methods: Forty-eight post spaces prepared in human lower premolars were applied with four dual-cure one-step self-etching adhesives Estelite Core Quick: ECB/ECQ, Clearfil DC Core Automix: CDB/CDC, Unifil Core EM: UNB/UNC, BeautiCore: BTB/BTC as the manufacturers' instructions. These adhesives were cured with light activation for 10 s, or chemical activation with 0, 10, and 30 s waiting intervals prior to placing resin core material. Resin core materials were then placed into the post space and light-cured for 60 s. After 24 h water storage, each specimen was serially sliced into 8, 0.6 mm x 0.6 mm thick beams for the mu TBS test. The regional mu TBS data were analyzed using three-way ANOVA and Dunnett's T3 test (p < 0.05).
Results: For the chemical activation with 10 and 30 s waiting intervals, ECB and CDB exhibited significantly improved mu TBS, whereas for UNB and BTB, the mu TBS were not significantly different but increased with waiting interval. On the other hand, light-activation of all the adhesives produced significantly higher mu TBS to root canal dentin than chemical activation (p < 0.05), except for the UNB group.
Conclusions: For the chemical activation of dual-cure one-step self-etching adhesives, a waiting interval prior to placing resin core material improved mu TBS to root canal dentin. Polymerising the adhesives before polymerisation reaction of resin core material would be effective for bonding to root canal dentin.
Clinical relevance: For chemical activation mode as well as light activation mode, pre-curing of adhesive layer before proceeding polymerisation of resin filling material would produce higher bonding performance to dentin in the cavity. (C) 2012 Elsevier Ltd Elsevier B.V. All rights reserved.